This invention relates to a liquid solution for coating substrates that demonstrates long-term stability cell adhesion properties and, more particularly, to a solution including a cross-linked amino acid polymer for applying to cytological specimen slides.
Many diagnostic assays depend on the evaluation of cytological and histological components. One requirement of these evaluations is the adhesion of these components to a solid substrate, such as a glass or plastic microscope slide. Once immobilized by adhesion, these components may be processed further to gain diagnostic information.
Several cytological/histological adhesion reagents have been developed and used in the past, such as albumin, silane, gelatin, and poly l-lysine. Although all are effective adhesive reagents to some degree, their adhesive properties do not remain stable once coated, applied, and dried on a solid substrate. This results in the need to prepare freshly coated slides for optimal routine use.
The present invention provides a solution of a cross-linked polymer for substrates. The solution includes an amino acid polymer, a buffered cross-linking agent, and deionized water (DI H2O).
In one embodiment, the amino acid polymer, as employed in the invention, is selected from a neutral or basic amino acid, such as but not limited to poly l-lysine or poly 1-arginine.
In another embodiment, the amino acid polymer, as employed in the invention, comprises poly l-lsine.
In another embodiment, the amino acid polymer, as employed in the invention, comprises poly l-lsine of molecular weight of 100,000 or higher.
In another embodiment, the cross-linking agent, as employed in the invention, comprises an aldehyde functional group.
In another embodiment, the cross-linking agent, as employed in the invention, comprises a buffered formaldehyde solution.
In one aspect, the present invention provides a cytological/histological adhesion reagent that retains its adhesive properties in a stable fashion when applied to a solid substrate such as a microscope slide.
In another aspect of the invention, it has been found that poly l-lysine is a suitable cytological adhesion reagent when applied and dried on a glass slide, but that its adhesive properties degraded fairly quickly over time. Poly l-lysine is a three dimensional helical polymeric molecule with side chains containing amine functional groups which effect its adhesive properties. With respect to one aspect of the invention, it was postulated that the physical degradation of this three-dimensional helical structure effectively negated the adhesive abilities of these side chain functional groups. In an attempt to retain this adhesive property of the poly l-lysine coated slides, the concept of stabilizing the poly l-lysine molecule structure was considered a viable solution.
In another aspect of the invention, a stabilization process is provided to cross-link the poly l-lysine molecule using formaldehyde. It is believed that the formaldehyde molecules link the functional groups on the end of the side chains back into the molecular framework, thus physically stabilizing the three-dimensional structure.